A human fetus—much less a human embryo—is, in fact, not an organism
Oh boy, here we go. By every biological definition, a embryo/zygote/fetus prior to the gestation period of 6 months (when it could theoretically live on it’s own) is a parasite. Yes, it robs the host of nutrients, it robs the host of oxygen, and it produces toxic waste withing the host. Most importantly, it cannot survive on it’s own—it’s wholly dependant on a host to live. By every biological aspect, it’s a parasite.